1. Field of the Invention
The invention relates to a process for laminating textile sheet materials onto moldable particle foam or onto foamed moldings, using a polymer composition as an adhesive.
2. Background Art
The trend toward increasingly lightweight components for use in motor vehicles and aircraft, and also in products for sport and leisure, has led to the development of foamed moldings with high mechanical stability and the greatest possible reduction in weight. To produce these foamed moldings, successful use has been made of materials such as expandable polystyrene (EPS) or expandable compositions based on EPS and polyphenylene oxide (PPO). The latter is available, for example, with the trade name Noryl® EF (registered trademark of General Electric Co. USA).
These compositions, such as EPS, EPE (expandable polyethylene) and EPP (expandable polypropylene) can be foamed with steam in suitable molds to give the desired moldings. This process known per se permits convenient production of moldings for interior automotive trim, for example door paneling, side-impact cushioning, knee cushioning, cores for headrests, sun visors and parcel shelves, and also for external applications, such as bumpers. Examples of applications unrelated to motor vehicle construction are sports products, such as surfboards.
However, some of the applications listed above cannot be exploited using the foamed parts by themselves. High requirements—for example for visual quality or for a high minimum level of dimensional stability and also low thermal expansion—mean that the foamed moldings have to be coated with an outer skin.
The usual flexible films are used here, with or without a foam backing, and in particular textiles or fiber webs. The latter are permeable to water vapor and are placed into the appropriate molding tool prior to the actual foaming-on procedure. A process of this type is termed in-mold skinning and is described, for example, in the GE Plastics brochure Noryl® EF—Profile (page 19). To provide adhesion here between the foam and the fiber web, use is made of hot-melt adhesives, the activation temperature of which must not be higher than the glass transition temperature of the foam material. Using these adhesives it is not, of course, possible to obtain high heat resistance in the laminates, in particular above 80° C. (since the adhesives soften).
EP-A 623491 has disclosed a material for automotive bodywork paneling components, composed of a foam core enclosed in a tube. The tube here is adhesive-bonded to the foam core or secured to it using heat.
Another in-mold skinning process for a door-paneling support is described in EP-A 710578. Here, a glass-fiber mat is placed into the molding tool prior to the actual foaming process, and the expanding foam is foamed onto a glass web without the need for any binder. However, this process, too, gives unsatisfactory strength of the glass-web/foam bond at temperatures above 80° C.